Since the office pays 720 dollars monthly
Since the office gives a 10% commission on the amount of selling
Then Donald will earn = 720 + 10% of x
Where x is the amount of selling
Since the amount of selling is 28800 dollars for the last month, then
Then x = 28800
[tex]S=720+\frac{10}{100}(28800)[/tex]Then
[tex]\begin{gathered} S=720+2880 \\ S=3600 \end{gathered}[/tex]Then Donald earned last month 3600 dollars